Replacing timing cover and oil pan gasket...order?

Definitely do the pan last. That front pan end seal will fight you if the pan's bolted up tight. Even with the pan left loose on the bolts the fat seal can be a real pain trying to keep the sealer that you use on the seal from getting all messed up if you're trying to position the cover in place to get the bolts to line up before tightening down. Been there before. I once made a set of jack screws using the two bottom corner threaded cover holes to "pull" my timing cover down into place on the end seal to get me by till I could do it the "right" way with the pan off.